The present invention relates to an inspection method, an inspection system and an inspection apparatus. More particularly, the present invention relates to an inspection method, inspection system and inspection apparatus for inspecting an object to be inspected such as a wafer.
In manufacture of semiconductor devices, the presence or absence of defects on wafers in a manufacturing process, for example, peelings or flaws of a formed circuit pattern, scratches caused by polishing, and foreign particles such as etching residues is inspected to secure a high yield. When a defect is found in the inspection, causes of the defect are checked and measures for removing the causes are taken. In the thus performed inspection, if the defect cannot be highly accurately detected and a type of the detected defect cannot be appropriately determined, it is difficult to investigate the causes and accordingly, it is also difficult to take appropriate measures.
With relation to the wafer inspection, there has heretofore been used widely a method of inspecting the presence or absence of defects based on scattered light intensities and light receiving angles detected when irradiating a wafer surface with a laser beam. Further, there has also been proposed a method of respectively irradiating a specific part of a wafer with a laser beam from the directions approximately perpendicular to and oblique to its surface and comparing detected scattered light intensities with a predetermined reference value (discrimination line) to thereby discriminate between concave defects such as scratches or Crystal Originated Particles (COPs) and convex defects such as foreign particles adhered to a wafer surface see for example U.S. Pat. No. 6,798,504 and U.S. Pat. No. 7,187,438.
On a so-called CZ wafer currently used widely in manufacture of semiconductor devices, COPs are easily formed due to surface properties of the CZ wafer. Accordingly, in a case of using a wafer containing COPs in manufacture of semiconductor devices, the wafer inspection must be performed as follows. During the defect inspection, the COPs due to the wafer are accurately discriminated from defects such as foreign particles caused by some external factors in the manufacturing process, and the presence of COPs (the number of COPs and their positions) is grasped. At the same time, causes of the defects such as foreign particles discriminated from COPs are investigated and the investigation results are used for subsequent measures.
The method of discriminating between foreign particles and COPs includes a method of comparing scattered light intensities detected by laser beam irradiation at a predetermined angle with a predetermined discrimination line to thereby discriminate between foreign particles and COPs as described above. However, since the discrimination line is a line set by previously disposing standard particles each having a known particle size on a wafer and detecting scattered light intensities by laser beam irradiation at a predetermined angle to define a boundary between standard particles and COPs, the following problem occurs. When such a discrimination line is applied to the inspection of wafers having foreign particles generated in the manufacturing process, the defects may be regarded as COPs particularly near the discrimination line even though being actually foreign particles.
Further, in using a polished wafer, when similarly setting the discrimination line using standard particles in order to discriminate between foreign particles and scratches, there may arise the same problem as that in discriminating between foreign particles and COPs.